The corrosion behavior of a low alloy steel in simulated groundwater was investigated. The upward surface of the steel underwent more serious corrosion than the downward surface. The corrosion products formed on the upward and downward surfaces were characterized by SEM, EDX, and XRD, and the electrochemical properties of bare and rusted samples were analyzed. The difference in the corrosion rates of the different surfaces of the steel could be attributed to the potential difference between the upward and downward surfaces as well as the higher amount of CaCO3 deposits on the downward surface leading to a compact corrosion product. (C) 2015 Elsevier B.V. All rights reserved.